Earth compacting apparatus



Oct. 14, 1969 'r. w. NEVITT, SR 3,472,135

EARTH COMPACTING APPARATUS Filed Oct. 23, 1967 2 Sheets-Sheet United States Patent 3,472,135 EARTH COMPACTING APPARATUS Tom W. Nevitt, Sr., Emporia, Kans, assignor to Nevitt Manufacturing Company, Inc., Emporia, Kans., a corporation of Kansas Filed Oct. 23, 1967, Ser. No. 677,202 Int. Cl. E01c 19/38 US. Cl. 94-49 9 Claims ABSTRACT OF THE DISCLOSURE An earth compacting machine employs a plurality of in-line tamper sections, each section comprising a reciprocable tamper member which is pinned to one end of an oscillatable beam. The opposite end of the beam is pivotally secured to the frame of the machine, and power is transmitted to the beam through a mechanism suspended therefrom between the pivotal connections.

The mechanism is reciprocated by an eccentric drive and includes a pair of depending arms between which a pair of end-to-end coil springs are disposed. The lower ends of the arms are joined to a reciprocable assembly which rides on an eccentric cam, the interconnection between the arms and the reciprocable assembly being effected by two pairs of pivotal links which operate in a push-pull fashion. The links move alternately to opposite sides of dead center at the top and the bottom of the travel of the eccentric cam to impart a driving force to the tamper at both ends of its stroke through the release of energy stored in the springs.

This invention relates to improvements in earth compacting apparatus for use primarily in the construction of highways, dams and the like where it is desired to compact an earth fill.

The principal object of the invention is to provide an earth compacting machine having a high cyclic rate of operation and which is capable of delivering a high tamping force against the material being compacted.

As a corollary to the foregoing object, it is an important aim of the instant invention to provide such a machine in which driving force is applied to a vertically reciprocable tamper at both ends of the stroke thereof in order to increase the force delivered against the material under compaction.

A further and important object of the invention is to provide a machine as aforesaid having a push-pull linkage mechanism between the prime mover and the tamper which lengthens the stroke of the latter to, in turn, increase the tamping force as mentioned above.

Still another important object of the invention is to provide a machine as aforesaid which stores energy during reciprocation of the tamper and delivers such energy thereto at both ends of the stroke of the tamper, thereby imparting driving force to the tamper as it moves downwardly into engagement with the earth as well as during upward movement thereof.

In the drawings:

FIGURE 1 is a front elevational view of the machine;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a partial top plan view;

FIG. 4 is an enlarged, vertical sectional view taken along line 44 of FIG. 1;

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 4;

FIG. 6 is a horizontal sectional view taken along line 66 of FIG. 4; and

FIGS. 7-10 are diagrammatic views illustrating the operation of the apparatus.

A rectangular base frame 20 is normally generally hori- Patented Oct. 14, 1969 zontally disposed and supports three uprights 22 positioned along the rear of frame 20 at the center and corners thereof. Three diagonal braces 24 extend from the front of base frame 20 to the upper ends of corresponding uprights 22, the latter being spanned by a top frame member 26. As illustrated by the broken lines in FIG. 2, a suitable linkage 28 may be connected to the rear of the framework for the purpose of securing the machine to the front of a wheeled or tracked pusher vehicle (not shown). Manifestly, the attitude of the machine and the spacing of the same above ground level may be controlled by the linkage 28.

The composite framework carries eight identical tamping assemblies 30, each assembly 30 including an oscillatable beam 32, an elongated reciprocable tamping member 34, and a tamping foot 36 rigid with the bottom end of member 34. Each member 34 may be of tubular or solid rod stock and is received within an upright guide sleeve 38 pivotally mounted on the front of base frame 20. The eight members 34 are spaced along the front of frame 20 at even intervals as seen in FIG. 1 to present a straight eight or in-line configuration.

Each of the guide sleeves 38 pivots about a horizontal axis defined by a pair of opposed axles 40 extending from sleeve 38 and rotatably carried by a pair of forwardly projecting, juxtaposed cars 42 on base frame 20. Member 34 is freely slidable within sleeve 38, the upper end of each member 34 being pivotally joined to the forward end of the corresponding beam 32 by a clevis and pin connection 44. The rearward ends of the beam 32 are pinned to the top frame member 26 for swinging, oscillatory movement about a horizontal axis.

The eight tamping assemblies 30 are driven by a prime mover 46 (FIG. 2) illustrated as comprising a hydraulic motor mounted on the rear of base frame 20 and coupled to a lineshaft 48 by a belt and pulley assembly 50. The lineshaft 48 extends substantially the length of base frame 20 from side-to-side, and is journalled at its ends and center in bearings 52 mounted on frame 20. An eccentric drive is utilized to transmit power from shaft 48 to a linkage mechanism 54 associated with each of the tamping assemblies 30 respectively.

Specifically, referring particularly to FIG. 4, each mechanism 54 comprises a pair of elongated elements or arms 56 having their upper ends joined to beam 32 by the hinge 58 of a pivotal suspension which is rigidly secured to beam 32 approximately midway along its length. Each of the elements 56 is in the form of a depending arm having approximately a 35 bend just below its midpoint. Pushpull structure in the nature of two pairs of opposed links 60 interconnects the lower ends of each of the elements 56 with a reciprocable assembly 62. A pair of pivot pins 64 join the outer ends of the pairs of links 60 to the lower ends of the elements 56, and a pair of pivot pins 66 join the inner ends of the links 60 to the assembly 62. Thus, movement of the elements 56 toward and away from each other is permitted as well as up-and-down movement of elements 56 as links 60 pivot about the axes of the inner pins 66.

The assembly 62 comprises a bearing unit surrounding an eccentric cam 68 keyed to shaft 48 and is provided with an upstanding boss portion 70 which supports an upright projection in the form of a guide rod 72. A pair of end-to-end coil springs 74 are in partial compression between the two elements 56, each spring 74 being held between a corresponding element 56 and a support component 76 which slidably receives rod 72 and is loosely carried thereby.

In FIG. 5 it may be seen that each of the elements 56 is transversely T-shaped and formed at its upper end to present a hinge barrel 78 receiving the hang pin 58. Each element 56 is also cutaway at its upper end through onehalf of its width to permit the two hinge barrels 78 to work freely without the two elements 56 interfering with each other. The hinge pin 58 is aligned with the axis of reciprocation of assembly 62, and may be adjustably positioned beneath beam 32 to control the leverage obtained by the latter by virtue of an adjustable clamp assembly 80 which forms a part of the suspension and embraces the beam 32.

Eight eccentric cams 68 are spaced along shaft 48 to drive the eight mechanisms 54, the various cams 68 being indentical in configuration but keyed to the shaft 48 in angularly spaced relationship to one another. Beginning at the left side of the apparatus as viewed in FIG. 1, the cam 68 of the first tamping assembly 30 is illustrated in the top position thereof as is clear in FIG. 4. All of the tamping feet 36 are shown hanging freely with the fourth foot 36 from the left side of the apparatus just touching the ground. In order to provide even timing and reduce the force reaction transmitted to the pusher vehicle, the cam 68 driving the sixth tamping assembly 30 is A; of a revolution behind the cam 68 associated with the first tamping assembly 30 illustrated in FIG. 4, i.e. the key on shaft 48 for the sixth cam 68 is disposed of a revolution behind the key for the first cam 68. Such spacing extends in order to the third, eighth, fourth, seventh, second and fifth cam 68 from the left end of the machine as viewed in FIG. 1 so that, in effect, an impact order of 1, 6, 3, 8, 4, 7, 2, 5, is produced, the numbers of the order corresponding to the order of the tamping assemblies 30 as viewed from left-to-right in FIG. 1. Therefore, each tamping foot 36 strikes the ground once during each revolution of shaft 48, but each impact is spaced in time from the preceding or the succeeding impact by A; of a revolution.

In operation, the apparatus is mounted on the front of a pusher vehicle by the linkage 28 and is pushed over the surface to be compacted, the lateral edges of the tamping feet 36 (except for the outside edges of the outside feet 36) being angnlarly disposed with respect to the line of travel to assure that the entire surface will be covered during a given pass. Since the operation of each of the individual tamping assemblies 30' and mechanisms 54 is identical, the operation of one tamper through a complete stroke will now be discussed with reference to FIGS. 4 and 7-10.

The diagrammatic illustration of cam 68 and links 60 in FIG. 7 corresponds to the full-line illustration of the apparatus in FIG. 4. The cam 68 is shown as it just reaches its top position. Note that the links 60 droop or extend downwardly from the inner pins 66 under the weight of the tamping assembly 30 which has been forced upward to the full-line position thereof by the prime mover 46.

When the apparatus is inoperative and hence the tamping assembly 30 is stationary, the weight of the latter compresses springs 74 somewhat as elements 56 are forced inwardly toward each other. The springs 74 are further compressed, however, during upward movement of mechanism 54 when the apparatus is in operation, because of the inertia of the relatively heavy tamping assembly 30 which must be overcome by the drive. Thus, when cam 68 reaches its top position, the springs 74 will be under increased compression and hence will have accumulated energy.

In FIG. 8, it may be noted that the links 60 are shown swinging about the inner pins 66 to upwardly inclined positions with cam 58 still shown as being at the top position. This is to illustrate that the links move to the opposite side of their dead center position at this time because, when the cam 68 reaches its top position, the momentum now attained by the tamping assembly 30 carries it further upwardly, and this momentum is augmented by the release of stored energy from the springs 74. Thus, as the cam 68 reaches its top position and commences downward movement, the tamping assembly 30 and mechanism 54 continue to move in an upward direction under the combined effects of momentum and the energy of the springs 74.

It should be understood at this juncture that use of the term dead center herein refers to the positions of the links 60 when the same are aligned in end-to-end relationship; this is not to be confused with the two dead center positions of the cam 68 occurring at the upper and lower limits of its travel.

FIGURE 9 shows cam 68 as it approaches the lower limit of its travel. During downward movement of the cam 68 from its FIG. 8 position, the cam 68 (and hence the prime mover 46) began exerting a pull on the mechanism 54 once the links had pressed over the dead center position. In other words, the fall of cam 68 under the drive of the prime mover 46 is more rapid than the acceleration of gravity which, of course, would ultimately of itself cause the tamping assembly 30 to drip into engagement with the ground. In the instant invention, however, the effect of gravity is augmented by the pulling action of the links 60 which again causes compression of springs 74 and the storage of energy therein as as the case during upward movement of mechanism 54.

The ultimate objective is illustrated in FIG. 10 where it may be seen that, as the cam 68 passes through its bottom position and no longer exerts a downward pulling force on links 60, the latter again move through the dead center position under both the force of gravity and the release of the energy stored in springs 74 during downward movement of mechanism 54. (The broken line represen tation of FIG. 4 illustrates the positions of the various moving parts of the apparatus when cam 68 is at its lowermost position and shows the links 60 as they are returning to a downwardly extending attitude as diagrammatically portrayed in FIG. 10). Therefore, the springs 74 impart driving force to the tamping assembly 30 in addition to the acceleration of gravity to increase the force of the tamping foot 36 against the earth to be compacted. Furthermore, the length of the stroke of the tamping member 34 is increased by the over-center action of links 60.

Another advantage of the instant invention is that, during a pause in tamping operation, motion of the tamping members 34 may be stopped without complete shutdown of the apparatus. An idle condition with the prime mover 46 still in operation is assumed by tilting the front of the apparatus downwardly until all of the tamping feet 36 are held in engagement with the ground. At this time, the various mechanisms 54 continue to reciprocate, but the beams 32 remain substantially at the position illustrated in full lines in FIG. 4 since the slack is taken up by the motion of links 60 and the action of springs 74.

The force exerted by each of the tampers of the instant invention has been measured in actual tests for a machine employing a foot 36 having a surface area of one square foot, a tamper member 34 having a length of 5', and a beam 32 approximately 34" in length between the centers of the pivots; (FIG. 4 is a scale drawing of an individual tamper section of essentially the same design as the machine tested). This produced an overall weight of the tamping assembly 30 on the order of 200 pounds. With a length of stroke of member 34 of 18 to 20 inches produced by a cam 68 rotating at a speed of between and r.p.m., the force exerted with foot 68 operating against the rigid base was 8850 pounds. The base consisted of a concrete slab protected by a 2 x 12 inch wooden plank.

The force measurement above and subsequent data to be set forth hereinbelow were obtained by attaching SR-4 strain gauges to the tamper member 34 above the foot 36, a brush recorder being utilized to graphically record the resulting strains. The cross-sectional area of the tamper member 34 was measured, and the measured strains were transformed into pounds of force by means of Hookes Law. A value of the modulus of elasticity of 30x10 lb./ sq. inch was used in the calculations.

The force exerted by a compacting machine in operation is greatly atfected by the properties of the material being compacted, If the machine acts against a mass which is relatively rigid, the force will be extremely high and the corresponding displacement very low. Conversely, if the material is deformable and springy the displacement will be large, and the corresponding force relatively low. Thus, operating the foot 36 against an undisturbed cinder-filled plot, the maximum impact force produced was 6195 pounds. In a third test, a hole two feet deep and approximately 18" in diameter was excavated and then level filled with loose material. The maximum impact force against such material during the initial stroke was approximately 1700 pounds. Then, after the soil removed during excavation was entirely replaced, and as consolidation took place, the maximum impact force rose to 4425 pounds.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In earth comparting apparatus: a pair of spaced-apart, reciprocable assemblies;

tamping means on one of said assemblies; driving means operably connected with the other of said assemblies for reciprocating the latter; and mechanism interconnecting said assemblies, said mechanism including: a pair of relatively movable elements coupled with said one assembly, push-pull structure between said elements connecting the latter with said other assembly for moving the elements relatively during reciprocation of said other assembly, and energy storage means coupled with and yieldably biasing said elements in one direction relatively, said structure being disposed for movement alternately to opposite sides of dead center whereby to impart a driving force to said one assembly at both ends of the stroke of said other assembly, said one assembly including an elongated, reciprocable member having said tamping means thereon, and an oscillatable beam for transmitting motion from said mechanism to said member. 2. The invention of claim 1, said elements depending from and being pivotally connected with said beam. 3. The invention of claim 1, said structure comprising a air of opposed links in end-to-end alignment when on dead center, said links pivotally connecting the elements with said other assembly and extending laterally from the other assembly in opposite directions. 4. The invention of claim 1, said energy storage means being interposed between said elements and loosely carried by said other assembly. 5. The invention of claim 1, said elements having pivotal suspension means above said other assembly in alignment with the axis of reciprocation of the latter.

6. The invention of claim 5,

said structure comprising a pair of opposed links in end-to-end, horizontal alignment when on dead center,

said links connecting the elements at the lowermost ends of the latter with said other assembly,

said links extending laterally from the other assembly in opposite directions,

7. The invention of claim 6,

said other assembly having an upstanding projection between the elements,

said energy storage means comprising a pair of endto-end springs between the elements having support means therebetween loosely carried by said projection.

8. The invention of claim 6,

said other assembly including a vertically reciprocable unit,

said driving means including a rotatable eccentric for reciprocating said unit.

9. In earth compacting apparatus:

a pair of spaced-apart, reciprocable assemblies;

tamping means on one of said assemblies;

driving means operably connected with the other of said assemblies for reciprocating the latter; and

mechanism interconnecting said assemblies,

mechanism including:

a pair of relatively movable elements coupled with said one assembly,

push-pull structure between said elements connecting the latter with said other assembly for moving the elements relatively during reciprocation of said other assembly, and

energy storage means coupled with an yieldably biasing said elements in one direction relatively,

said structure being disposed for movement alternately to opposite sides of dead center whereby to impart a driving force to said one assembly at both ends of the stroke of said other assembly,

said one assembly including an oscillatable beam,

said elements having pivotal suspension means on said beam and above said other assembly in alignment with the axis of reciprocation of the latter.

said

References Cited UNITED STATES PATENTS 988,367 4/1911 McHench 94-49 X 2,098,895 11/1937 Velten 9449 2,903,948 9/ 1959 Simmonds 9449 3,181,442 5/1965 Brigel 9449 X NILE C. BYERS, 112., Primary Examiner 

